Digital Infrastructure and Green Innovation for Urban Sustainability: Evidence from the Perspective of Innovation Structure

Digital infrastructure is increasingly regarded as a key enabler of economic modernization and urban sustainability, but its sustainability implications depend on whether digitalization guides innovation activities toward greener technological directions. Against the backdrop of China’s “dual carbon” goals and the deepening of low-carbon transformation, this study examines the relationship between digital infrastructure development and the green orientation of urban innovation from the perspective of innovation structure. Using panel data for 284 prefecture-level cities in China from 2011 to 2023, we measure the share of green innovation by the proportion of green invention patents in total granted patents, and use broadband Internet access users per 100 residents, denoted as InternetRate, as a proxy for digital infrastructure development. A two-way fixed effects model is employed to investigate the empirical relationship between the two. The results show that digital infrastructure development is significantly negatively associated with the relative share of green innovation within total innovation. This finding remains robust to alternative functional-form specifications, extreme-value treatment, alternative measures of digital infrastructure, and alternative measures of green innovation structure, and remains directionally consistent in a supplementary instrumental-variable test. Decomposition of scale effects indicates that this negative association reflects the relatively faster expansion of non-green innovation rather than an absolute contraction in green innovation, suggesting a structural reallocation pattern within urban innovation activities. Heterogeneity analysis shows that the negative association is mainly concentrated in cities with lower levels of economic development and higher text-based environmental governance attention, and is more pronounced in cities with a lower degree of industrial servitization. Moderation analysis further shows that this negative association becomes weaker in cities with stronger local green fiscal support. Spatial analysis indicates that the share of green innovation exhibits significant spatial dependence; however, the association between digital infrastructure development and innovation structure is mainly localized, with no significant spatial spillover detected. These findings contribute to sustainability research by showing that digital infrastructure does not automatically improve the green composition of innovation and that sustainable digital transformation requires complementary green fiscal support, environmental governance, and industrial upgrading policies.